This invention relates in general to the field of programming, and more particularly to using a high level programming language with a smart card or a microcontroller.
Software applications written in the Java high-level programming language have been so designed that an application written in Java can be run on many different computer brands or computer platforms without change. This is accomplished by the following procedure. When a Java application is written, it is compiled into "Class" files containing byte codes that are instructions for a hypothetical computer called a Java Virtual Machine. An implementation of this virtual machine is written for each platform that is supported. When a user wishes to run a particular Java application on a selected platform, the class files compiled from the desired application is loaded onto the selected platform. The Java virtual machine for the selected platform is run, and interprets the byte codes in the class file, thus effectively running the Java application.
Java is described in the following references which are hereby incorporated by reference: (1) Arnold, Ken, and James Gosling, "The Java Programming Language," Addison-Wesley, 1996; (2) James Gosling, Bill Joy, and Guy Steele, "The Java Language Specification," Sun Microsystems, 1996, (web site: http://java.sun.com/doc/language_specification); (3) James Gosling and Henry McGilton, "The Java Language Environment: A White Paper," Sun Microsystems, 1995 (web site: http://java.sun.com/doc/language_environment/); and (4) Tim Lindholm and Frank Yellin, "The Java Virtual Machine Specification," Addison-Wesley, 1997. These texts among many others describe how to program using Java.
In order for a Java application to run on a specific platform, a Java virtual machine implementation must be written that will run within the constraints of the platform, and a mechanism must be provided for loading the desired Java application on the platform, again keeping within the constraints of this platform.
Conventional platforms that support Java are typically microprocessor-based computers, with access to relatively large amounts of memory and hard disk storage space. Such microprocessor implementations frequently are used in desktop and personal computers. However, there are no conventional Java implementations on microcontrollers, as would typically be used in a smart card.
Microcontrollers differ from microprocessors in many ways. For example, a microprocessor typically has a central processing unit that requires certain external components (e.g., memory, input controls and output controls) to function properly. A typical microprocessor can access from a megabyte to a gigabyte of memory, and is capable of processing 16, 32, or 64 bits of information or more with a single instruction. In contrast to the microprocessor, a microcontroller includes a central processing unit, memory and other functional elements, all on a single semiconductor substrate, or integrated circuit (e.g., a "chip"). As compared to the relatively large external memory accessed by the microprocessor, the typical microcontroller accesses a much smaller memory. A typical microcontroller can access one to sixty-four kilobytes of built-in memory, with sixteen kilobytes being very common.
There are generally three different types of memory used: random access memory (RAM), read only memory (ROM), and electrically erasable programmable read only memory (EEPROM). In a microcontroller, the amount of each kind of memory available is constrained by the amount of space on the integrated circuit used for each kind of memory. Typically, RAM takes the most space, and is in shortest supply. ROM takes the least space, and is abundant. EEPROM is more abundant than RAM, but less than ROM.
Each kind of memory is suitable for different purposes. Although ROM is the least expensive, it is suitable only for data that is unchanging, such as operating system code. EEPROM is useful for storing data that must be retained when power is removed, but is extremely slow to write. RAM can be written and read at high speed, but is expensive and data in RAM is lost when power is removed. A microprocessor system typically has relatively little ROM and EEPROM, and has 1 to 128 megabytes of RAM, since it is not constrained by what will fit on a single integrated circuit device, and often has access to an external disk memory system that serves as a large writable, non-volatile storage area at a lower cost than EEPROM. However, a microcontroller typically has a small RAM of 0.1 to 2.0 K, 2K to 8K of EEPROM, and 8K-56K of ROM.
Due to the small number of external components required and their small size, microcontrollers frequently are used in integrated circuit cards, such as smart cards. Such smart cards come in a variety of forms, including contact-based cards, which must be inserted into a reader to be used, and contactless cards, which need not be inserted. In fact, microcontrollers with contactless communication are often embedded into specialized forms, such as watches and rings, effectively integrating the functionality of a smart card in an ergonomically attractive manner.
Because of the constrained environment, applications for smart cards are typically written in a low level programming language (e.g., assembly language) to conserve memory.
The integrated circuit card is a secure, robust, tamper-resistant and portable device for storing data. The integrated circuit card is the most personal of personal computers because of its small size and because of the hardware and software data security features unique to the integrated circuit card.
The primary task of the integrated circuit card and the microcontroller on the card is to protect the data stored on the card. Consequently, since its invention in 1974, integrated circuit card technology has been closely guarded on these same security grounds. The cards were first used by French banks as debit cards. In this application, before a financial transaction based on the card is authorized, the card user must demonstrate knowledge of a 4-digit personal identification number (PIN) stored in the card in addition to being in possession of the card. Any information that might contribute to discovering the PIN number on a lost or stolen card was blocked from public distribution. In fact, since nobody could tell what information might be useful in this regard, virtually all information about integrated circuit cards was withheld.
Due to the concern for security, applications written for integrated circuit cards have unique properties. For example, each application typically is identified with a particular owner or identity. Because applications typically are written in a low-level programming language, such as assembly language, the applications are written for a particular type of microcontroller. Due to the nature of low level programming languages, unauthorized applications may access data on the integrated circuit card. Programs written for an integrated circuit card are identified with a particular identity so that if two identities want to perform the same programming function there must be two copies of some portions of the application on the microcontroller of the integrated circuit card.
Integrated circuit card systems have historically been closed systems. An integrated circuit card contained a dedicated application that was handcrafted to work with a specific terminal application. Security checking when an integrated circuit card was used consisted primarily of making sure that the card application and the terminal application were a matched pair and that the data on the card was valid.
As the popularity of integrated circuit cards grew, it became clear that integrated circuit card users would be averse to carrying a different integrated circuit card for each integrated circuit card application. Therefore, multiple cooperating applications began to be provided on single provider integrated circuit cards. Thus, for example, an automated teller machine (ATM) access card and a debit card may coexist on a single integrated circuit card platform. Nevertheless, this was still a closed system since all the applications in the terminal and the card were built by one provider having explicit knowledge of the other providers.
The paucity of information about integrated circuit cards--particularly information about how to communicate with them and how to program them--has impeded the general application of the integrated circuit card. However, the advent of public digital networking (e.g., the Internet and the World Wide Web) has opened new domains of application for integrated circuit cards. In particular, this has lead to a need to load new applications on the card that do not have explicit knowledge of the other providers, but without the possibility of compromising the security of the card. However, typically, this is not practical with conventional cards that are programmed using low level languages.